Given that schools totally fail at these, can't we consider making children do something else. Something which does not involve sitting in classrooms for 8 hours a day and learning nothing?

I learned plenty in primary and secondary school. So has my son, who is about to graduate high school and attend university in the fall. Perhaps you went to bad schools, or the school's environment just didn't fit you. That's an argument for better and more adaptable schools, not a condemnation of the concept of mandatory public education.

The moment I entered university I learned much more and much faster. Obviously the fault for that lies with the school system.

My school was an average school for students targeting a university degree and I did quite well compared to my peers.

The foundation you needed to even attend university was set during basic schooling. As much as you think you "learnt nothing" I don't think there's a way for you to have gone through university by learning absolutely nothing in basic schooling.

Should schools be reformed to better align to contemporary ways of living? Of course, I'm all onboard to have a better education system, finding ways to foster kids inherent curiosities in a less strict and authoritarian way, finding new systems that are both scalable while being more free for kids to pursue their interests at their own rate, and finding a way where every kid might have a decent shared baseline of knowledge to go on into their adult lives.

It doesn't mean tearing down all education, or that current education is useless and teaches nothing. It's inadequate but it's the most valuable asset any society can have, finding better ways to do it is a natural progression to improve it.

I wish the education system had allowed me to not waste countless hours in classrooms listening to lectures that I either had already learned through autodidacticism, or that I wasn't interested in at that moment in time, I had to "re-learn" a bunch of material that was presented in classrooms but I was too uninterested to focus on it at that moment. Still, I don't think it was a total failure, just an education model with flaws that needs to be fixed.

My point is that for the 12 years I was at school, I actually learned very little.

To be clear, I am not against "learning", quite the opposite. I want children to learn effectively.

But how do you even judge that? You have a dataset of n=1 with no control. Besides, wouldn't you expect to learn 'more effectively' with a young adult's brain than a pre-adolescent one, particularly if you were getting the right level of attention from a teacher and the pace of study was being accelerated as you moved through primary and secondary school?